The present invention relates to a battery module control system and a battery module control method which are used to control a battery module including one or more battery cells.
It is expected that, as awareness of environmental problems grows, vehicles driven by electric motors, such as electric vehicles (EV) and hybrid electric vehicles (HEV), systems that store electricity generated from sunlight, or the like will rapidly become popular. In such vehicles and electricity storage systems, lithium ion batteries, nickel-metal hydride batteries, lead batteries or any other secondary batteries are used. In the future, it is expected that large amounts of batteries used once in the vehicles or electricity storage systems will be collected. Various measures for effectively reusing the collected, used batteries are now under consideration.
By the way, as is commonly said, when a plurality of batteries connected are used, it is prohibited to use batteries that are different in degradation level, capacity and other characteristics in such a way that the batteries are connected in parallel. The reason is that, when the charge and discharge associated with a reverse current between batteries become large, the reverse current involves risks, such as heat generation. Accordingly, when batteries that are different in capacity characteristics are connected in parallel and used, safety needs to be guaranteed by means of a reverse current prevention function or the like. However, even when the reverse current prevention function is provided, large variations in capacity between batteries could lead to dependence on a battery having the worst degradation level (or a small capacity). Therefore, it tends to be impossible to extract the original capacity.
Depending on usage histories, the batteries are different in degradation level, capacity and other characteristics. Therefore, when a battery module is reused, it is necessary to somehow acquire data about the collected battery module. The methods to acquire the data have been so far proposed.
For example, what is disclosed in Patent Document 1 (JP-A-2007-141464) is a battery information management device, which includes a battery information storage section that stores, as battery information, at least electrical characteristic information of the battery information management device or usage history information and which is connected to a secondary battery module, with the battery information management device also including: an information processing section, which is so formed as to contain at least a CPU and a memory; an output section, which outputs an information processing result by the information processing section; and an interface section, which connects the secondary battery module to the information processing section. The information processing section uses the interface section to read the battery information, which is stored in the battery information storage section of the secondary battery module, and classifies the battery information according to grade on the basis of one or more threshold values that are separately defined in advance and of the battery information read in order to reuse the secondary battery module. The classified-by-grade information, which is obtained as a result of classifying according to grade, is output to the output section. The battery information management device also includes a battery information database, which accumulates the battery information read by the interface section in such a way that the battery information becomes associated with identification information of the secondary battery module that outputs the battery information.
According to what is disclosed in Patent Document 1, it is necessary to provide the secondary battery module with the battery information storage section, in which the battery information, such as electrical characteristic information of the battery information management device or usage history information, is stored, or to provide the device with a section that reads the battery information stored in the battery information storage section. Therefore, the problem is that the configuration required to reuse the secondary battery module becomes extremely complicated and expensive. Moreover, the reusable secondary battery module is provided with the battery information storage section that complies with the standards as described above. Therefore, the problem is that an arbitrary secondary battery module cannot be reused.